DNA barcoding of billfishes

Abstract

DNA barcoding is a method promising fast and accurate identification of animal species based on the sequencing of the mitochondrial c oxidase subunit (COI) gene. In this study, we explore the prospects for DNA barcoding in one particular fish group, the billfishes (suborder Xiphioidei—swordfish, marlins, spearfishes, and sailfish). We sequenced the mitochondrial COI gene from 296 individuals from the 10 currently recognized species of billfishes, and combined these data with a further 57 sequences from previously published projects. We also sequenced the rhodopsin gene from a subset of 72 individuals to allow comparison of mitochondrial results against a nuclear marker. Five of the 10 species are readily distinguishable by COI barcodes. Of the rest, the striped marlin (Kajikia audax) and white marlin (K. albida) show highly similar sequences and are not unambiguously distinguishable by barcodes alone, likewise are the three spearfishes Tetrapturus angustirostris, T. belone, and T. pfluegeri. We discuss the taxonomic status of these species groups in light of our and other data, molecular and morphological.

Keywords::

• COI
• rhodopsin
• mitochondrial DNA
• species delimitation

Declaration of interest: This work was supported through funding to the Canadian Barcode of Life Network from Genome Canada (through the Ontario Genomics Institute), NSERC, and other sponsors listed at http://www.BOLNET.ca; and additionally by operational funds to the Guy Harvey Research Institute, AFTCO, Inc., and an NSERC postgraduate fellowship (AB). We thank L. Beerkircher, J. Graves, J. McDowell, E. Prince, J. Serafy, and D. Snodgrass for providing tissue samples and Eugene Wong for assistance in the laboratory. We are grateful to Johanne Fischer of the FAO for granting permission to use images from their catalog (Nakamura 1985) for the first figure in our study. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.